1. Field of the Invention
This invention relates to systems for cooling electronic devices, and particularly to systems for cooling high-power devices on a direct-bonded copper (DBC) substrate.
2. Description of the Related Art
Power dissipation in electronic circuits remains an important design consideration and is becoming more important as performance for such circuits is becoming thermally limited. For example, a power module having multiple high power devices sitting on a substrate needs to be cooled to prevent overheating and damage to the devices as well as to better-ensure long term reliability of the devices and their power connections. Many high power modules in commercial and military use are liquid cooled by forcing liquid flow through a pin fin base plate (cold plate), with the pin fins increasing the heat transfer surface area from an otherwise flat base plate. (See U.S. Pat. Nos. 6,594,149, 7,042,725, 7,417,857, 7,353,859). Unfortunately, such systems are limited by the cooling capability (h) of the forced convection and by thermal resistance over the base plate and solder layer. Other cooling solutions include evaporative spray cooling on custom-made base plates that have surface structures to enhance the heat transfer. (See U.S. Pat. No. 6,993,926 and US 2009/0014562). Such systems tend to be comparatively bulky and costly, however. Use of DBC substrates to mount high power devices in combination with direct impingement liquid cooling has been found to improve thermal resistance over the base plate and solder layer, but the no-fin DBC solutions suffer from substantial loss in back-side cooling surface area and so thermal dissipation is greatly limited by the liquid impingement flow rate. (See U.S. Pat. No. 7,190,581) Macro-scale fins may be attached DBC substrates, but such macro-scale fins block the liquid impingement path and are not made with commercially available DBC substrates thus adding cost to the total system solution.
A need still exists to provide for greater power dissipation for high power devices seated in power modules with more-uniformity of temperature among such devices while maintaining a compact and cost-effective system structure.